The present invention relates to an automotive infinite transmission and, more particularly, to an improvement in drive blocks that are movable within effective diameters of pulleys.
In a conventional automotive infinite transmission, as shown in, for example, U.S Pat. No. 3,720,113, a V-belt is entrained around opposed inside surfaces of a pair of respective pulley members and one of the pair of pulley members is axially movable, so that the rotational position of the V-belt is continuously changed to enable the transmission ratio to be continuously varied.
In the infinite transmission of this type, since both sides of the V-belt must be held by the friction against the opposed inside surfaces or flanks of the pair of pulley members, it is impossible to excessively reduce the frictional coefficient of the sides of the V-belt. On the other hand, when the transmission ratio is desired to be changed, the V-belt must be slid in the radial direction along the confronted flanks of the pulley members in response to the axial movement of the one pulley member. Therefore when the transmission ratio is changed, considerably high pressure is applied to both the side faces of the V-belt. Thus, the conventional infinite transmission suffers a durability problem in the V-belt.
Also, in U.S. Pat. No. 4,295,836, there is proposed another infinite transmission in which a plurality of drive elements are interposed between a pair of guide disks each having therein spiral slits, and a flat belt are laid around and on the drive elements.
In the above U.S. patent, pins provided at both ends of each of the drive elements are engaged with the slits of the respective guide disks, and the pins are fixedly located at predetermined positions by changing the relative angular position between the pair of guide disks. Therefore, upon changing the transmission ratio, twist stresses will be applied to the pins, which causes the durability problem. Also, when the spiral slits are formed in the guide disks, a considerably high working or maching precision will have to be required.